Sheep Brain Anatomy

Structures Seen in External View of Sheep Brain

The external view of the sheep brain reveals several key anatomical structures that are essential for understanding brain organization and function. These structures are commonly identified in laboratory practicals.

• Dura mater: The tough, outermost meningeal layer protecting the brain.

• Cerebrum: The largest part of the brain, responsible for higher brain functions such as thought and action.

• Gyri: Elevated ridges on the brain surface that increase surface area.

• Sulcus: Shallow grooves between gyri.

• Longitudinal fissure: Deep groove dividing the left and right cerebral hemispheres.

• Transverse fissure: Separates the cerebrum from the cerebellum.

• Corpus quadrigemina: Four colliculi involved in visual and auditory reflexes.

• Cerebral peduncle: Bundles of nerve fibers connecting the cerebrum to the brainstem.

• Mammillary body: Part of the limbic system, involved in memory processing.

• Pituitary gland: Endocrine gland controlling various hormonal functions.

• Optic chiasm: X-shaped structure where optic nerves cross.

• Olfactory bulbs: Structures involved in the sense of smell.

• Cerebellum: Coordinates voluntary movements and balance.

• Brainstem: Includes midbrain, pons, and medulla oblongata; controls vital functions.

• Pons: Relays signals between cerebrum and cerebellum.

• Medulla oblongata: Regulates heart rate, breathing, and other autonomic functions.

• Spinal cord: Transmits neural signals between brain and body.

• 4th ventricle: Cavity containing cerebrospinal fluid (CSF).

• Corpus callosum: Large bundle of fibers connecting the two cerebral hemispheres.

• Lateral ventricle: Cavity within each cerebral hemisphere containing CSF.

• Choroid plexus: Network of cells producing CSF.

• Thalamus: Relay station for sensory information.

• Hypothalamus: Regulates homeostasis, including temperature and hunger.

• Pineal gland: Secretes melatonin, regulating sleep cycles.

Structures Seen in Sagittal View of Sheep Brain

The sagittal view (a cut along the midline) allows visualization of internal brain structures.

• Cerebellum: As above, coordinates movement and balance.

• Arbor vitae: Tree-like arrangement of white matter in the cerebellum, important for signal transmission.

Blood Vessels Supplying the Brain

Blood supply to the brain is critical for delivering oxygen and nutrients. Several major arteries and vascular structures are involved.

• Internal carotid arteries: Major arteries supplying blood to the brain.

• Vertebral arteries: Supply blood to the posterior part of the brain.

• Basilar artery: Formed by the union of vertebral arteries; supplies the brainstem and cerebellum.

• Circle of Willis: Circular arterial structure providing collateral blood flow to the brain.

Structures Shown on the Model of the Ventricles

The ventricular system consists of interconnected cavities filled with cerebrospinal fluid (CSF), which cushions and nourishes the brain.

• Lateral ventricles: Paired cavities in each cerebral hemisphere.

• Third ventricle: Midline cavity between the two halves of the thalamus.

• Cerebral aqueduct: Narrow channel connecting third and fourth ventricles.

• Fourth ventricle: Located between the brainstem and cerebellum.

• Central canal of spinal cord: Continuation of the ventricular system into the spinal cord.

Summary Table: Major Structures and Their Functions

Key Terms and Definitions

• Gyri: Raised folds on the surface of the brain.

• Sulci: Grooves between gyri.

• Ventricle: Cavity within the brain filled with cerebrospinal fluid.

• Arbor vitae: White matter in the cerebellum, resembling a tree.

• Choroid plexus: Structure that produces cerebrospinal fluid.

Example: Flow of Cerebrospinal Fluid (CSF)

CSF is produced in the choroid plexus of the lateral ventricles, flows through the third ventricle via the interventricular foramen, passes through the cerebral aqueduct to the fourth ventricle, and then enters the central canal of the spinal cord and subarachnoid space.

Formula: